This invention relates to a skimmer-boom apparatus for skimming and diverting a floating liquid pollutant such as oil from a body of water.
Historically, the most effective way of controlling the movement of a liquid pollutant which is spilled on a body of water and which floats on the surface thereof, has been to use floating barriers, commonly referred to as booms, to confine the pollutant to a collection area. A boom is generally a floating, elongated mechanical device used to divert or stop the flow of a floating liquid pollutant. Devices presently on the market suffer from several failure mechanisms, a number of which follow: Underflow caused by currents or waves carries the pollutant outside of the collection area. Splashover, caused by waves, carries the pollutant over the boom device and outside the collection area. Mechanical failure of the structural members or joints of conventional boom devices causes complete loss of control of the pollutant. Anchoring and positioning problems may be encountered when fixing the booms in place to cause inefficient collection of the pollutant.
Generally, booms may be classified into containment devices and diversionary devices. Either class of booms may be anchored in a body of water or towed through a body of water, but both become ineffective in controlling the movement of pollutants when the relative velocity of the water with respect to the boom exceeds approximately one knot for containment devices and two knots for diversionary devices. Since currents in excess of one or two knots are frequently encountered and skimmers are being designed to operate in currents up to ten knots, the need for a pollutant collection device which will be effective in currents in excess of two knots is obvious.
Numerous oil collecting and containing devices appear in the prior art. U.S. Pat. No. 3,650,406 issued to Brown et al describes a collect in system having a floating weir as one section and a boom as another section. A flexible sheet, in combination with the two aforementioned sections, forms a catch basin for collecting the oil. This system is adapted for towing through a body of water. U.S. Pat. No. 3,886,750, issued to Ayers et al describes an oil-containment apparatus for use in water experiencing high current velocities. An upstream and downstream barrier connected with a partially permeable membrane define a capture area such that flow velocity therein is reduced. This allows oil to float to the surface to enable collection devices to remove the oil from the capture area. Flow velocity is reduced by using a membrane of sufficient permeability such that flow out of the capture area is less than the volume of water approaching the inlet. Water is deflected beneath the collection device as the velocity of flow at the inlet increases. However, a certain amount of oil floating atop the water would necessarily be carried underneath the device with the diverted flow, the amount of oil increasing with the velocity of flow. U.S. Pat. No. 4,096,700, issued to Muramatsu et al describes a device similar to the Ayers device in that an upstream and a downstream barrier are connected together by a perforated, flexible sheet. The oil flows into the containment apparatus through inlet openings in the upstream barrier and a plurality of outlet openings are arranged in the flexible sheet such that the outlet area is greater than the inlet area. A guide plate made integral with the flexible sheet serves to guide the film of oil into the inlet openings. The ratio of the inlet opening area to the outlet opening area is chosen to eliminate turbulence within the collection area. However, since flow is allowed to escape from the device through the outlet openings, a certain amount of oil will be carried into the device and out of the outlet openings with the water, the amount increasing with the velocity of flow-through. In other words, instead of losing oil beneath the device as in Ayers, oil is lost through the underwater outlet of the Muramatsu device. In addition, since the guide plate will be fixed in relation to the upstream barrier as an integral part of the flexible sheet, if the oil film is a greater thickness than the distance from the water surface to the guide plate, a portion of the oil film will be deflected beneath the Muramatsu device. Because of their velocity sensitivity, the efficiency of the prior art devices tends to decrease drastically as the velocity of flow-through increases.